Re: [SI-LIST] : May 9th Presentation: "Radiation from Edge Effects in Printe...

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From: Ritchey Lee ([email protected])
Date: Mon May 15 2000 - 10:51:22 PDT

Mike,

Do you have any controlled experimental measurements to support these
rules that
you can share with us? By that I mean before and after measurements
where the
only thing done was to add one structure at a time, such as the chassis
ground
ring or the resonance spoiler capacitors?

Lee

[email protected] wrote:

> Lawrence:
>
> Re: Your copper tape suggestion.
>
> Yes, it does work. I have been preaching this technique since 1989 to all my
> clients in the form of a "chassis ground ring" on every layer of the PCB with
> vias at varying spaces (to prevent high harmonic resonances along the edge)
> to create a reasonably low inductance field termination structure for fields
> emanating from all inboard locations on the PCB. I use this technique, along
> with several others to achieve typical reductions of >20 dB in radiated
> emissions. Because the slot created along the edge of any surface plane (or
> fill) may be inadvertently excited to radiate, mounting provisions for
> "resonance spoiler" capacitors should be placed along the slot. These
> capacitor provisions allow "doctoring" of the structure if emission problems
> are found and avoid another board spin.
>
> The setback approach (20-H is a bit arbitrary) has its place in small, high
> packaging density boards that can't afford the real estate for a separate
> ring.
>
> Mike
>
> Michael L. Conn
> Owner/Principal Consultant
> Mikon Consulting
>
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